Numerous publications of tank washing machines already exist. Usually these machines rotate homogeneously about a vertical axis, whilst the nozzles making homogeneous or oscillating movements about a horizontal axis. Mostly the machines are driven by a turbine or a motor. The movement pattern of the nozzles is determined by a set of mechanical parts. A serious disadvantage is these machines are spreading the cleaning fluid in all directions with approximately the same intensity. The furthest places being jetted under the sharpest impingement angle receive relatively the smallest amount of washing water. Sometimes it is necessary to give special attention to places with a more rigid kind of contamination, such as the rim of burn-yeast in brewery tanks. The bottle-neck in the cleaning of the tank depends on the places receiving the smallest amount of washing water and having the most rigid kind of pollution. Most of its operational time conventional machines are spraying washing water to places that were already cleaned.
In many cases sanitation first needs spreading of a concentrated cleaning or disinfection agent. After a certain soaking time this agent and the contamination can be removed using fresh water. Usually in these cases the room is cleaned manually. In principle the existing tank washing machines are capable of spreading these agents, in practice, however, the high flow rates and the long time necessary to reach a complete coverage result in needed quantities of cleaning agent being so high, that their use is normally not economical.